PDF13: Providing replacement text using the /Alt entry for links in PDF
documents

Important Information about Techniques

See Understanding Techniques for WCAG Success Criteria for important information about the usage of these informative techniques and how they relate to the normative WCAG 2.0 success criteria. The Applicability section explains the scope of the technique, and the presence of techniques for a specific technology does not imply that the technology can be used in all situations to create content that meets WCAG 2.0.

User Agent and Assistive Technology Support Notes

Description

The objective of this technique is to provide replacement link text
via the /Alt entry in the property list for a tag. This is usually
not necessary, but in some situations, additional information beyond
the visible link text is needed, particularly for screen reader users.
Screen readers can read visible link text, but replacing the screen
text with meaningful alternate text for links in a PDF document can
make links more accessible.

Links in PDF documents are represented by a Link tag and objects in
its sub-tree, consisting of a link object reference (or Link annotation)
and one or more text objects. The text object or objects inside the
Link tag are used by assistive technologies to provide a name for the
link.

Authors can replace the default link text by providing an /Alt entry
for the Link tag. When the Link tag has an /Alt entry, screen readers
ignore the value of any visible text objects in the Link tag and use
the /Alt entry value for the link text.

The simplest way to provide context-independent link text that complies
with the WCAG 2.0 success criteria is to create them when authoring
the document, before conversion to PDF. In some cases, it may not be
possible to create the links using the original authoring tool. When editing PDF documents with Adobe Acrobat Pro, the best way to create accessible links is to use the Create Link command.

Authors should make sure that the alternate text makes sense in context
of the screen text before and after the link.

Tests

Procedure

For the hyperlink, verify that the alternate link text is properly
coded by one of the following:

Read the PDF document with a screen reader, listening to hear
that the alternate link text is read correctly.

Use a tool that is capable of showing the /Alt entry to open
the PDF document and view the hyperlink and alternate link text.

Use a tool that exposes the document through the accessibility
API and verify that the alternate link text is the text for the
link.

Expected Results

#1 is true.

If this is a sufficient technique for a success criterion, failing this test procedure does not necessarily mean that the success criterion has not been satisfied in some other way, only that this technique has not been successfully implemented and can not be used to claim conformance.